1. Field of the Invention
The present invention is directed generally to ceiling fans with metal contoured blades for controlling the direction of the air flow. More specifically, the present invention is directed to metal contoured blades utilizing rolled back edges to comply with accepted safety standards for ceiling fans.
2. Description of Prior Art
Many contoured blades are well known in the art of propeller and air blades as used in connection with water craft, air exhaust fans and air circulating floor fans. The prior art is exemplified by U.S. Pat. Nos. 1,506,937; 3,609,055; 3,124,681; 4,892,460; and 1,818,607. However, none of the above patents discloses the specific metal fan with a special contour as constituted by applicant's invention. By way of example U.S. Pat. No. 4,892,460 discloses a ceiling fan having a fan blade 2 with a trailing edge to which an auxiliary blade 1 is attached; note that the auxiliary blade 1 is merely arcuate and is not contoured like applicant's invention and that this patented fan would not operate in the reverse direction, that the blade 24 is twisted at its free end 27, and that such blade does not utilize a constant contour as used by applicant.
U.S. Pat. No. 3,174,681 discloses a reversible propeller wherein each blade has an S-shaped cross section which is not constant but rather varies from the central hub to the tip thereof.
U.S. Pat. No. 2,609,055 shows a reversible propeller blade having opposite sides which are not S-shaped and which are constructed by two separate sections that are joined together.
U.S. Pat. No. 1,506,937 relates to a fan blade which is twisted along its longitudinal axis and which has a contour that is not constant but rather varies along such axis.
U.S. Pat. No. 1,818,607, granted Aug. 11, 1931, to Elba E. Campbell, discloses a fan blade comprising two metal stampings (12, 14) riveted together to form four blades (18). A central flat portion (20) serves as a hub for the fan, which may be used to cool automobile engines or the like. The forward or leading edge (24) of the blade is bent out of the plane of the flat blade, while the trailing edge (25) is bent slightly upwardly into the plane of the fan. The bent edges stiffen the fan blade, but eliminate, or at least reduce, the whistling noise of the rotating fan blade.
Whereas contoured metal blades have found widespread acceptance for use in ceiling fans employed in rooms with ceilings of approximately eight feet in height, or greater, safety considerations have precluded usage of metal fan blades in low height applications. Underwriters Laboratories established a safety standard for ceiling fans approximately twelve years ago, and such standard is predicated upon the thickness of wooden paddle fan blades, which are typically three-sixteenths of an inch thick at the forward "impact" edge of the blade.
Metal blades, be they made as flat metal stampings, or as contoured, S-shaped blades, are considerably thinner than three-sixteenths of an inch, thus the potential harmful impact of rapidly rotating metal blades upon persons and property coming into contact with the blades posed a serious safety hazard. Consequently, the safety standard established by Underwriters' Laboratories, and implemented by the ceiling fan industry, has precluded the utilization of ceiling fans with metal blades for low height applications. The wooden paddle blade fan, despite disadvantages of weight, speed, longevity of operation, etc. when compared to ceiling fans with contoured metal blades, has obtained a heretofore unchallenged domination of the ceiling fan market for low height applications.